Coating can provide one or more protective layers for the underlying substrate and can also have an aesthetically pleasing value. A typical coating finish over a substrate can comprise some or all of the following coating layers: (1) one or more primer layers that provide adhesion and basic protection, and also cover minor surface unevenness of the substrate; (2) one or more colored layers, typically pigmented, that provide most of the protection, durability and color; and (3) one or more clearcoat layers that provide additional durability and improved appearance. A colored topcoat layer can be used in place of the colored layer and clearcoat layer. These coatings can be used on buildings, machineries, equipments, vehicles as automotive original equipment manufacture (OEM) and refinish coatings, or in other coating applications.
The coatings are typically formed from coating compositions which can be solvent borne or waterborne. Solvent borne coating compositions typically contain volatile organic compounds (VOC) that are compounds of carbon, which can emit into atmosphere and participate in atmospheric photochemical reactions. Many volatile organic compounds are commonly used in industrial products or processes, such as solvents, dispersants, carriers, coating compositions, molding compositions, cleaners, or aerosols. VOCs emitted into atmosphere, such as those emitted from coating compositions during coating manufacturing, application and curing process, can be related to air pollution impacting air quality, participate in photoreactions with air to form ozone, and contribute to urban smog and global warming.
Waterborne coating compositions are desirable due to their low VOC contents. However, waterborne coating compositions can have limitations in terms of storage, processing and handling. There are continuing needs for improved waterborne coating compositions.